α-Elimination of organic halides from organotellurium(IV) halides

Three types of α-elimination (oxidative, photolytic, and thermal) of organotellurium(IV) halides to give organic halides have been disclosed. Treatment of organotellurium(IV) halides with some oxidants, preferably t-butyl hydroperoxide, in 1,4-dioxane, acetic acid, or acetonitrile affords the corresponding organic halides in good yields with retention of configuration and by ipso-replacement. The reactivity order of this α-elimination is roughly as follows: alkyl > aryl > alkenyl. The main reaction course seems to be a 1,2-tellurium halogen shift in unstable organotellurium(VI) compounds formed in situ by oxidation. Similar α-elimination also occurs by photolysis of these compounds with a high-pressure mercury lamp in benzene as the solvent. Here, a cross-coupling of the organic moiety with benzene scarcely occurs except for the cases of diaryltellurium(IV) dihalides. Neat pyrolysis of some alkyl(phenyl)tellurium(IV) dibromides at 200–250 °C (Kugelrohr distillation apparatus) again results in α-elimination to produce the corresponding alkyl bromides almost quantitatively.     

Cu(II) 2-quinoxalinol salen catalyzed oxidation of propargylic,benzylic, and allylic alcohols using tert-butyl hydroperoxide in aqueous solutions

The synthesis of carbonyl compounds by oxidation of alcohols is a key reaction in organic synthesis. Such oxidations are typically conducted using catalysts featuring toxic metals and hazardous organic solvents. Considering green and sustainable chemistry, a copper(II) complex of sulfonated 2-quinoxalinol salen (sulfosalqu) has been characterized as an efficient catalyst for the selective oxidation of propargylic, benzylic, and allylic alcohols to the corresponding carbonyl compounds in water when in combination with the oxidant tert-butyl hydroperoxide. The reactions proceed under mild conditions (70 °C in water) to produce yields up to 99% with only 1 mol % of catalyst loading. This reaction constitutes of a rare example of propargylic alcohol oxidation in water, and it makes this process greener by eliminating the use of hazardous organic solvents. Excellent selectivity was achieved with this catalytic protocol for the oxidation of propargylic, benzylic, and allylic alcohols over aliphatic alcohols. The alcohol oxidation is thought to go through a radical pathway.     

Use of a Simple Additive Scheme to Predict the GC Retention Indices of Aromatic Compounds with Different Structures

A simple algorithm is proposed for prediction of linear retention indices, RI, of organic compounds with different structures. The algorithm is based on the hypothesis that any structural moiety of a molecule contributes to gas chromatographic retention to a different extent, depending on its molecular environment. For a given moiety the mean structural increment (MSI) is calculated from the difference between the retention indices of two molecules, one containing it and one not, in different compound families. The mean of these values is the MSI for the corresponding moiety. The correlation between predicted and experimental values affords r ² = 0.992 and the mean relative error is 1.65% for n = 92 compounds.     

Triptycene-derived calixarenes,heterocalixarenes and analogues

With unique three-dimensional triptycene derivatives as the building blocks, several kinds of novel macrocyclic compounds including triptycene-derived calixarenes, heterocalixarenes, N(H)-bridged azacalixarenes, homooxacalixarene analogues, and tetralactam macrocycles could be conveniently synthesized with satisfactory yields by one-pot method or two-step fragment coupling reactions. With rigid triptycene moiety, these macrocyclic hosts not only have large enough cavities, but also show specific fixed conformations. These structural features made them exhibit well molecular recognition toward small organic molecules, fullerenes and organic dyes. Moreover, these macrocycles could also show interest self-assembly abilities in both solution and solid state, which will make them be broad application prospects.     

Synthesis and study of new phenolic antioxidants with nitroaromatic and heterocyclic substituents

New polyfunctional aromatic, nitroaromatic, and heterocyclic compounds linked to the 2,6-di-tert-butylphenol moiety via –NH–, –C(O)NH–, –S–, or–C=N– spacers were synthesized. These structures provide intramolecular charge transfer (ICT) and exhibit antioxidant activity. The structures of the new compounds were established by X-ray diffraction. The novel compounds were evaluated for antioxidant activity using the DPPH assay. The presence of the 2,4,6-trinitrophenyl moiety in combination with the –NH– spacer leads to a considerable increase in the antioxidant activity of 2,6-di-tert-butylphenols. These compounds are also weak lipoxygenase inhibitors. The results of this study provide an opportunity to search for new types of antioxidants with ICT.     

Convenient synthesis of 3-unsubstituted oxindole-1-carboxamides

The multiple reactivity of the mesomeric anion formed by N- or C(3)-deprotonation of 3-unsubstituted oxindoles hampers the selective introduction of substituents onto the nitrogen atom. A conveniently applicable reaction sequence has been elaborated for the synthesis of 3-unsubstituted oxindole-1-carboxamides starting from the easily available 1,3-bis(phenoxycarbonyl)oxindoles. Selective amidation of the N-phenoxycarbonyl moiety and subsequent removal of the C(3)-phenoxycarbonyl moiety furnished the title compounds, which are useful building blocks for further functionalization. Besides the novel methodologies, several new representatives of this valuable compound family and their intermediates are also described below.     

Novel plant activators with thieno[2,3-d]-1,2,3-thiadiazole-6-carboxylate scaffold： Synthesis and bioactivity

The 1,2,3-thiadiazole-carboxylate moiety was reported to be an important pharmacophore of plant activators.In this study,a series of novel plant activators based on thieno[2,3-d]-1,2,3-thiadiazole-6-carboxylate were designed and synthesized and their biological activity as plant activators was studied.The structures of the novel compounds were identifed by1H NMR,19F NMR and HRMS.The in vivo bioassay showed that these novel compounds had good effcacy against seven plant diseases.Especially,compounds 1a and 1c were more potent than the commercialized plant activator BTH.Almost no fungicidal activity was observed for the active compounds in the in vitro assay,which matched the requirements as plant activators.     

Determination of Organic Peroxides by High Performance Liquid Chroma-Tography with Electrochemical Detection

Abstract

The application of electrochemical detection to the high performance liquid chromatographic determination of organic peroxides has been studied. The use of a buffered mobile phase was found to be critical to the successful analysis of samples containing hydroperoxides. Using amperometric detection, mixtures of peroxide containing compounds were readily determined. The sensitivity of the amperometric detector was in the one nanogram range for both benzoyl peroxide and cumene hydroperoxide. Polar-ographic detection was found to be a highly reproducible method for the analysis of samples containing peroxides as components of mixtures in the range of 5-2000 ng. The peroxide containing compounds determined in this manner were t-butyl hydroperoxide, cumene hydroperoxide, and 13-hydroperoxy-9(Z)-11(E)-octadecadien-oic acid. The polarographic detection system was used to obtain observed half-wave potentials for the peroxides under different chromatographic conditions. These observations correlated closely with literature results on the polarography of these compounds.     

Selective oxidation of hydroxy groups of phenylthio and phenylseleno alcohols

Various kinds of alcohols bearing phenylthio or phenylseleno moiety were converted into the corresponding carbonyl compounds in good to excellent yields by treating with dimesityl diselenide and $\text{tert}$-butyl hydroperoxide.     

Two New Aristolochic Acid Analogues from the Roots of Aristolochia contorta with Significant Cytotoxic Activity

Twelve compounds, including two new aristolochic acid analogues with a formyloxy moiety (9–10) and 10 known aristolochic acid derivates (1–8 and 11–12), were obtained from the roots of Aristolochia contorta. Their structures were elucidated using extensive spectroscopic methods. Their cytotoxic activity in human proximal tubular cells HK-2 was evaluated by the MTT method, which has been widely used to assess cell viability. Among these molecules, compounds 3 and 9 were found to be more cytotoxic. Furthermore, molecular modeling was used to evaluate, for the first time, the interactions of compounds 3 and 9 with the target protein organic anionic transporter 1 (OAT1) that plays a key role in mediating aristolochic acid nephropathy. Structure–activity relationships are briefly discussed.     

A dichotomy in the enantioselective oxidation of aryl benzyl sulfides: A combined experimental and computational work

Pentafluorobenzyl pentafluorophenyl sulfide is oxidised with moderate e.e. value and a low yield by the usually highly successful oxidation protocol based upon tert-butyl hydroperoxide (TBHP) in the presence of a titanium/hydrobenzoin complex. This disappointing result resisted until the present work, in which the switch of the oxidation agent (from TBHP to cumene hydroperoxide), suggested by our previous computations, yielded the enantiopure sulfoxide. This valuable chiral compound was obtained in good yields (76%) without resorting to a chromatographic separation. DFT computations uncovered that this favourable reactivity was originated by a stabilizing π?π?stacking between the phenyl group of the oxidant and the pentafluorophenyl moiety of the substrate.     

Synthesis of new chiral fluorescent sensors and their applications in enantioselective discrimination

Five novel sensors (R,R)-3–6 and (S, S)-6 were synthesized and developed for enantioselective recognition of chiral compounds. Sensor 6 with two thiourea groups and steric π-conjugation frameworks could discriminate different chiral substrates, including acidic compounds, basic compounds, and neutral compounds. These results disclosed that the outstanding performance of enantioselective discrimination could be attributed to the thiourea group which acted as a hydrogen-bonding donor and the bulky steric moiety of the hosts which provided appropriate chiral environment. This result will be of great practical value in the designation of chiral sensors and high-throughput assay of chiral products.     

Modular Synthetic Approach to Carboranyl‒Biomolecules Conjugates

The development of novel, tumor-selective and boron-rich compounds as potential agents for use in boron neutron capture therapy (BNCT) represents a very important field in cancer treatment by radiation therapy. Here, we report the design and synthesis of two promising compounds that combine meta-carborane, a water-soluble monosaccharide and a linking unit, namely glycine or ethylenediamine, for facile coupling with various tumor-selective biomolecules bearing a free amino or carboxylic acid group. In this work, coupling experiments with two selected biomolecules, a coumarin derivative and folic acid, were included. The task of every component in this approach was carefully chosen: the carborane moiety supplies ten boron atoms, which is a tenfold increase in boron content compared to the l-boronophenylalanine (l-BPA) presently used in BNCT; the sugar moiety compensates for the hydrophobic character of the carborane; the linking unit, depending on the chosen biomolecule, acts as the connection between the tumor-selective component and the boron-rich moiety; and the respective tumor-selective biomolecule provides the necessary selectivity. This approach makes it possible to develop a modular and feasible strategy for the synthesis of readily obtainable boron-rich agents with optimized properties for potential applications in BNCT.     

Participation of ethyl 3-formylindole-2-carboxylate with the Ugi four-component condensation reaction

Multicomponent condensation of ethyl 3-formylindole 2-carboxylate, amines, isocyanide and (S)-N-boc-alanine or (S)-N-boc-serine is described. This Ugi four-component condensation (Ugi-4CC) reaction yielded a series of novel dipeptides containing an indolyl moiety. These compounds exhibit potential biological activity.     

Synthesis and Olfactory Properties of Seco-Analogues of Lilac Aldehydes

Lilac aldehydes are considered as principal olfactory molecules of lilac flowers. We have designed, prepared, and evaluated a set of racemic seco-analogues of such natural products. The synthesis employs commercially available α-chloroketones as substrates that are transformed in four steps to target compounds. Their qualitative olfactory analysis revealed that the opening of the tetrahydrofuran ring leads to a vanishing of original flowery scent with the emergence of spicy aroma accompanied by green notes, and/or fruity aspects of novel seco-analogues. These results suggest the important osmophoric role of THF moiety for the generation of the typical flowery aroma associated with lilac aldehydes.     

Determination of lipids and their oxidation products by IR spectrometry

We proposed a procedure for the IR spectrometric determination of lipid hydroperoxides in biological systems. The main bands in the IR absorption spectra of linoleic acid and its hydroperoxide were identified, and analytical bands suitable for the determination of both compounds in their mixtures were selected. It was demonstrated that tert-butyl hydroperoxide can be used as an external standard for determining fatty acid hydroperoxides. Using the external standard method (calibration curve) for tert-butyl hydroperoxides, we calculated the concentration of linoleic acid hydroperoxide in its mixture with linoleic acid; it agreed with the specified values. Using the developed procedure, we estimated the concentration of hydroperoxide groups in natural cardiolipin. The results were compared to those obtained by an independent method (activated chemiluminescence).     

Synthesis of chiral iodo-N,O-acetonide aminal scaffolds via an efficient cascade reaction of amino acid-derived epoxides

Novel amino acid-derived iodo-N,O-acetonide aminals were developed as chiral, non-epimerizable scaffolds to facilitate complex molecule synthesis. These scaffolds are readily prepared from commercially available amino acid derivatives in ?6 steps, contain an orthogonally-protected β-hydroxy amine moiety, and feature a directly reactive alkyl-iodide group for facile substitution chemistry. Further, a novel ring opening/cyclization cascade reaction was developed to prepare these compounds efficiently (59-72%) from readily available epoxide derivatives.     

A simple accurate model for prediction of deflagration temperature of energetic compounds

A novel general method is introduced to predict deflagration temperature of organic energetic compounds containing at least –NNO₂, –ONO₂, or –CNO₂ groups. Deflagration temperature is an important safety parameter in working with dangerous energetic compounds and their environmental problems. It is shown that the contribution of some molecular structure parameters can be used to interpret thermal decomposition of an energetic compound. For 86 energetic materials (corresponding to 102 measured values) with different molecular structures, the new correlation has the root mean square (rms) and the average deviations of 23.8 and 19.0 K, respectively. The new method is also tested for some energetic compounds with complex molecular structures, e.g., two new organic energetic molecules N,N′-bis(1,2,4-triazol-3yl)-4,4′-diamino-2,2′,3,3′,5,5′,6,6′-octanitroazobenzene (BTDAONAB) and 2,4,6-trinitrophloroglucinol.     

Mimetics of the Selenoenzyme Glutathione Peroxidase: Novel Structures and Unusual Catalytic Mechanisms

Glutathione peroxidase (GPx) mimetics comprise an important class of selenium-containing antioxidants that catalyze the destruction of biologically harmful peroxides in the presence of stoichiometric thiol reductants. The synthesis of two novel cyclic selenium compounds and their evaluation as GPx mimetics was achieved. The first is a cyclic seleninate ester that is formed in situ from the oxidation of allyl 3-hydroxypropyl selenide. The second is a spirodioxyselenurane that is similarly formed from di(3-hydroxypropyl) selenide. Both compounds were shown to be remarkably active catalysts in an assay based on the reduction of t-butyl hydroperoxide with benzyl thiol. The mechanisms of the catalytic cycles of the two novel selenium compounds were elucidated and were found to be distinct from each other and from that of GPx.     

A novel approach to the synthesis of benzo[b]fluoren-11-ones

A novel intramolecular palladium-mediated arylation approach to benzo[b]fluoren-11-ones has been investigated. This approach involves the novel oxidation of the key starting 2-(2′-bromobenzyl)naphthols to 2-(2′-bromobenzyl)-1,4-naphthoquinones, followed by protection of the quinone moiety of the latter compounds and the final Pd-promoted bi-arylic cyclization of the resulting 2-(2′-bromobenzyl)-1,4-dimethoxynaphthalenes.